Institute of Electrical and Electronics Engineers (IEEE) is responsible for the standards that govern wireless communication. One such standard, IEEE 802.15.4, is a technical standard which defines the operation of low-rate wireless personal area networks (LR-WPANs). It specifies the physical layer and media access control for LR-WPANs. It is the basis for the ZigBee, ISA100.11a, WirelessHART, MiWi, SNAP, and Thread specifications, each of which further extends the standard by developing the upper layers which are not defined in IEEE 802.15.4. Alternatively, it can be used with 6LoWPAN, the technology used to deliver the IPv6 version of the Internet Protocol (IP) over WPANs, to define the upper layers.
IEEE standard 802.15.4 intends to offer the fundamental lower network layers of a type of wireless personal area network (WPAN) which focuses on low-cost, low-speed ubiquitous communication between devices. It can be contrasted with other approaches, such as Wi-Fi, which offer more bandwidth and require more power. The emphasis is on very low cost communication of nearby devices with little to no underlying infrastructure, intending to exploit this to lower power consumption even more.
The basic framework conceives a 10-meter communications range with a transfer rate of 250 kbit/s. Tradeoffs are possible to favor more radically embedded devices with even lower power requirements, through the definition of not one, but several physical layers. Lower transfer rates of 20 and 40 kbit/s were initially defined, with the 100 kbit/s rate being added in the current revision. Even lower rates can be considered with the resulting effect on power consumption. As already mentioned, the main identifying feature of IEEE 802.15.4 among WPANs is the importance of achieving extremely low manufacturing and operation costs and technological simplicity, without sacrificing flexibility or generality. Important features include real-time suitability by reservation of guaranteed time slots, collision avoidance through CSMA/CA and integrated support for secure communications. Devices also include power management functions such as link quality and energy detection.
IEEE 802.15.4-conformant devices may use one of three possible frequency bands for operation: 868.0-868.6 MHz, 902-928 MHz, and 2400-2483.5 MHz. IEEE 802.15.4 includes a Scan process, but that Scan process has several drawbacks as will be discussed below.
The IEEE 802.15.4 Scan process gives a device the ability to find a network, to associate to that network, and to disassociate from that network as necessary. It is possible, however, for unintended devices to join a given IEEE 802.15.4 network. During the 802.15.4 Scan process, used by a device to try to join an existing network, the device listens for beacons from active devices (PAN coordinators), which are transmitting them. System, network, and or channel conditions can cause devices to join or receive information from unintended networks in one of two ways. In the case of an active scan, the scanning device transmits a beacon request on a particular channel that could be received by active devices on a wrong channel. In the case of active as well as passive scans, the beacon response may be received on a channel different than what the active device transmitted it on.
In both cases the Media Access Control (MAC) layer reports this scan result to the upper layer stack using its current channel as it has no way of knowing if it was due to an erroneous condition. At this point the 802.15.4 Stack will start the association process based on information in the scan result having the incorrect channel Therefore, new systems, apparatus, and methods are needed that maximize the probability of successful and reliable scans to minimize unintended devices from joining a given IEEE 802.15.4 network, and additionally to join the network on the intended channel.
Accordingly, there is a need for systems, apparatus, and methods that overcome the deficiencies of conventional approaches including the methods, system and apparatus provided hereby.